package com.itlong.cloud.utils.random;
/**
 * Created by cuiduanwu on 2017/9/18.
 */

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

/**
 * 分布式逻辑ID
 *
 * @author cuiduanwu
 * @create 2017--18 10:07
 */

public class IdWorker {
    protected static final Logger LOG = LoggerFactory.getLogger(IdWorker.class);

    private final long workerId;

    private final static long twepoch = 1361753741828L;

    private long sequence = 0L;

    private final static long workerIdBits = 8L;

    public final static long maxWorkerId = -1L ^ -1L << workerIdBits;


    private final static long sequenceBits = 14L;

    private final static long workerIdShift = sequenceBits;

    private final static long timestampLeftShift = sequenceBits + workerIdBits;

    public final static long sequenceMask = -1L ^ -1L << sequenceBits;

    private long lastTimestamp = -1L;

    /** 初始化构造函数
     *
     * @param workerId  可变ID的长度
     */
    public IdWorker(final long workerId) {
        super();
        if (workerId > this.maxWorkerId || workerId < 0) {
            throw new IllegalArgumentException(
                    String.format("worker Id can't be greater than %d or less than 0", this.maxWorkerId));
        }
        this.workerId = workerId;
    }

    public synchronized long nextId() {
        long timestamp = this.timeGen();
        if (this.lastTimestamp == timestamp) {
            this.sequence = (this.sequence + 1) & this.sequenceMask;
            if (this.sequence == 0) {
                System.out.println("###########" + sequenceMask);
                timestamp = this.tilNextMillis(this.lastTimestamp);
            }
        } else {
            this.sequence = 0;
        }
        if (timestamp < this.lastTimestamp) {
            try {
                throw new Exception(String.format("Clock moved backwards.  Refusing to generate id for %d milliseconds",
                        this.lastTimestamp - timestamp));
            } catch (Exception e) {
                e.printStackTrace();
            }
        }
        this.lastTimestamp = timestamp;
        long nextId = ((timestamp - twepoch << timestampLeftShift)) | (this.workerId << this.workerIdShift)
                | (this.sequence);

        // System.out.println("timestamp:" + timestamp + ",timestampLeftShift:"

        // + timestampLeftShift + ",nextId:" + nextId + ",workerId:"

        // + workerId + ",sequence:" + sequence);
        return nextId;
    }
    private long tilNextMillis(final long lastTimestamp) {
        long timestamp = this.timeGen();
        while (timestamp <= lastTimestamp) {
            timestamp = this.timeGen();
        }
        return timestamp;
    }
    private long timeGen() {
        return System.currentTimeMillis();
    }
}
